U.S. Pat. No. 3,595,040 issued July 27, 1971 to R. D. Curl for a Handle Lock Attachment discloses a device which is securable to a molded case circuit breaker and is capable of receiving a padlock to maintain the elements of the lock attachment in operative position to limit movement of the circuit breaker operating handle. The handle lock attachment of the aforesaid Curl patent is secured to the circuit breaker housing by utilizing four screws which extend into apertures in the circuit breaker housing located around the periphery of the aperture through which the circuit breaker operating handle extends. Since the fastening screws are threaded directly into the molded housing of the circuit breaker it is relatively easy to rip the entire handle lock attachment from the circuit breaker and thereby defeat the intended purpose of the attachment.
The prior art has attempted to provide handle lock attachments that are mounted directly to molded case circuit breakers without utilizing fasteners, such as screws, which are driven into the molded housing. One such prior art attempt is illustrated in co-pending U.S. patent application Ser. No. 865,224, filed Dec. 28, 1977 entitled Bracket Means To Mount A Padlock For Blocking Movement of A Switch Handle, with R. C. Clement and W. R. Latimer as coinventers, and assigned to the assignee of the instant invention.
A drawback of the device of the aforesaid co-pending application Ser. No. 865,224 is that the circuit breaker must be constructed with particularly shaped and positioned undercuts which receive portions of the handle lock attachment. Further, the attachment must be manufactured to relatively close tolerances.